U.S. patent application number 15/951707 was filed with the patent office on 2019-01-31 for braze alloys for joining or repairing ceramic matrix composite (cmc) components.
The applicant listed for this patent is Rolls-Royce Corporation, Trustees of the Colorado School of Mines. Invention is credited to Sean Landwehr, Stephen Liu, Juan Carlos Madeni, Scott Nelson, Juan Wei, Raymond Xu.
Application Number | 20190031570 15/951707 |
Document ID | / |
Family ID | 65137888 |
Filed Date | 2019-01-31 |
![](/patent/app/20190031570/US20190031570A1-20190131-D00001.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00002.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00003.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00004.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00005.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00006.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00007.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00008.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00009.png)
![](/patent/app/20190031570/US20190031570A1-20190131-D00010.png)
United States Patent
Application |
20190031570 |
Kind Code |
A1 |
Nelson; Scott ; et
al. |
January 31, 2019 |
BRAZE ALLOYS FOR JOINING OR REPAIRING CERAMIC MATRIX COMPOSITE
(CMC) COMPONENTS
Abstract
A braze alloy for joining or repairing ceramic matrix composite
(CMC) components comprises a braze composition including silicon at
a concentration from about 48 at. % to about 66 at. %, titanium at
a concentration from about 1 at. % to about 35 at. %, and an
additional element selected from aluminum, cobalt, vanadium,
nickel, and chromium. The braze composition comprises a melting
temperature of less than 1300.degree. C.
Inventors: |
Nelson; Scott; (Carmel,
IN) ; Xu; Raymond; (Carmel, IN) ; Landwehr;
Sean; (Avon, IN) ; Wei; Juan; (Lakewood,
CO) ; Liu; Stephen; (Golden, CO) ; Madeni;
Juan Carlos; (Littleton, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rolls-Royce Corporation
Trustees of the Colorado School of Mines |
Indianapolis
Golden |
IN
CO |
US
US |
|
|
Family ID: |
65137888 |
Appl. No.: |
15/951707 |
Filed: |
April 12, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62485163 |
Apr 13, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 35/30 20130101;
C04B 37/003 20130101; C04B 2237/16 20130101; C04B 2237/365
20130101; C04B 37/006 20130101; C04B 2237/08 20130101; C04B 2237/38
20130101; C04B 2237/60 20130101 |
International
Class: |
C04B 37/00 20060101
C04B037/00; B23K 35/30 20060101 B23K035/30 |
Claims
1. A braze alloy for joining or repairing ceramic matrix composite
(CMC) components, the braze alloy comprising: a braze composition
comprising: silicon at a concentration from about 48 at. % to about
66 at. %; titanium at a concentration from about 1 at. % to about
35 at. %, and an additional element selected from the group
consisting of: aluminum, cobalt, vanadium, nickel, and chromium,
wherein the braze composition comprises a melting temperature of
less than 1300.degree. C.
2. The braze alloy of claim 1, wherein the melting temperature is
less than 1250.degree. C.
3. The braze alloy of claim 1, wherein the braze composition
comprises an alloy system selected from the group consisting of:
(a) silicon, aluminum and titanium, (b) silicon, cobalt, vanadium
and titanium, and (c) silicon, titanium, nickel, cobalt and
chromium.
4. The braze alloy of claim 1, wherein the braze composition is
silicon-rich with either aluminum, cobalt or titanium present at a
concentration ranging from about 27 at. % to about 36 at. %.
5. The braze alloy of claim 4, wherein the braze composition
includes aluminum at a concentration from about 32 at. % to about
36 at. %.
6. The braze alloy of claim 5, wherein the concentration of silicon
is from about 60 at. % to about 66 at. % and the concentration of
titanium is from about 2 at. % to about 4 at. %.
7. The braze alloy of claim 5, wherein the melting temperature lies
in a range from about 1150.degree. C. to about 1185.degree. C.
8. The braze alloy of claim 4, wherein the braze composition
includes cobalt at a concentration from about 27 at. % to about 30
at. %.
9. The braze alloy of claim 8, wherein the concentration of silicon
is from about 59 at. % to about 63 at. %, and the concentration of
titanium is from about 1 at. % to about 3 at. %.
10. The braze alloy of claim 8, wherein the braze composition
further comprises vanadium at a concentration of from about 7 at. %
to about 10 at. %.
11. The braze alloy of claim 8, wherein the melting temperature
lies in a range from about 1225.degree. C. to about 1260.degree.
C.
12. The braze alloy of claim 4, wherein the braze composition
includes titanium at a concentration from about 29 at. % to about
35 at. %.
13. The braze alloy of claim 12, wherein the braze composition
further comprises nickel at a concentration of from 7 at. % to
about 11 at. %, cobalt at a concentration of from about 4 at. % to
about 6 at. %, and chromium at a concentration of from about 3 at.
% to about 6 at. %.
14. The braze alloy of claim 12, wherein the concentration of
silicon is from about 48 at. % to about 52 at. %.
15. The braze alloy of claim 12, wherein the melting temperature
lies in a range from about 1270.degree. C. to about 1295.degree.
C.
16. The braze alloy of claim 1, wherein the braze composition
includes, upon brazing, at least one silicide phase.
17. The braze alloy of claim 1, wherein the at least one silicide
phase is selected from the group consisting of: TiSi.sub.2,
CoSi.sub.2, VSi.sub.2, (Ni,Co)Si.sub.2, (Ti,Cr)Si.sub.2, and
Ti.sub.4Ni.sub.4Si.sub.7.
18. A method of joining or repairing ceramic matrix composite (CMC)
components, the method comprising: placing a braze alloy having a
melting temperature less than 1300.degree. C. adjacent to and/or
between first and second components, at least one of the first and
second components comprising a ceramic matrix composite; heating
the braze alloy to a predetermined brazing temperature; after the
heating, cooling the braze alloy, thereby forming a brazed joint
between the first component and the second component, wherein the
braze alloy has a braze composition comprising silicon at a
concentration from about 48 at. % to about 66 at. %, titanium at a
concentration from about 1 at. % to about 35 at. %, and an
additional element selected from the group consisting of: aluminum,
cobalt, vanadium, nickel, and chromium.
19. The method of claim 18, wherein the predetermined brazing
temperature is in a range from about 1210.degree. C. to about
1350.degree. C.
20. The method of claim 18, wherein the braze composition comprises
an alloy system selected from the group consisting of: (a) silicon,
aluminum and titanium, (b) silicon, cobalt, vanadium and titanium,
and (c) silicon, titanium, nickel, cobalt and chromium.
Description
RELATED APPLICATION
[0001] The present disclosure claims the benefit of priority under
35 U.S.C. 119(e) to U.S. Provisional Patent Application Ser. No.
62/485,163, filed on Apr. 13, 2017, which is hereby incorporated by
reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates generally to a braze alloy,
and more specifically to a braze alloy for joining or repairing
components used in gas turbine engines.
BACKGROUND
[0003] Ceramic matrix composites (CMCs) may be used in aerospace
engine applications because of their mechanical properties and
chemical stability at high temperatures. Various components of gas
turbine engines, such as blades and vanes, can be manufactured from
CMCs, such as silicon carbide (SiC) fiber-reinforced SiC matrix
(SiC/SiC) composites.
[0004] Coupling together two or more components made of CMCs can be
challenging. Traditionally-used braze alloys based on nickel and/or
gold may exhibit undesirably low melting temperatures and/or have a
tendency to form low-melting point eutectic phases in braze joints
and areas adjacent to the braze joints due reactions with free
silicon in the CMC component. For example, a gold-based braze alloy
may interact with free silicon during brazing to form a
gold-silicon eutectic phase that has a melting temperature of about
360.degree. C. The resulting braze joint and surrounding areas may
then be susceptible to failure and oxidation at high temperatures
in use. As a result, such braze joints may not be suitable in high
temperature sections of gas turbine engines.
[0005] A challenge with brazing alloys designed for high
temperature applications is that the brazing temperature may be
close to the melting point of silicon in the CMC matrix. For
example, the brazing temperature of a current high temperature
braze alloy is about 1375.degree. C., which is only 39.degree. C.
below the melting point of silicon. A brazing cycle at 1375.degree.
C. has the potential of jeopardizing the microstructural integrity
and mechanical strength of the CMC.
[0006] It would advantageous to be able to carry out the brazing of
CMC components at lower temperatures without sacrificing the
mechanical properties and high temperature stability of the brazed
joint.
BRIEF SUMMARY
[0007] A braze alloy for joining ceramic matrix composites
comprises a braze composition including silicon at a concentration
from about 48 at. % to about 66 at. %, titanium at a concentration
from about 1 at. % to about 35 at. %, and an additional element
selected from aluminum, cobalt, vanadium, nickel, and chromium. The
braze composition has a melting temperature of less than
1300.degree. C. Preferably, the melting temperature is at least
about 1150.degree. C. The braze alloy may be used to bond together
ceramic matrix composite (CMC) components employed in gas turbine
engines.
[0008] A method of joining ceramic matrix composites comprises
placing a braze alloy having a melting temperature less than
1300.degree. C. adjacent to and/or between first and second
components, where at least one of the first and second components
comprises a ceramic matrix composite, and heating the braze alloy
to a predetermined brazing temperature, which is equal to or
greater than a melting temperature thereof. After the heating, the
braze alloy is cooled to form a brazed joint between the first
component and the second component. The braze alloy has a braze
composition comprising silicon at a concentration from about 48 at.
% to about 66 at. %, titanium at a concentration from about 1 at. %
to about 35 at. %, and an additional element selected from the
group consisting of: aluminum, cobalt, vanadium, nickel, and
chromium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A-1D are phase diagrams showing the impact of
aluminum additions on the silicon-titanium alloy system.
[0010] FIGS. 2A-2C are phase diagrams showing the impact of
vanadium additions on the silicon-cobalt alloy system.
[0011] FIGS. 3A-3C are phase diagrams showing the impact of
titanium on the silicon-cobalt-vanadium alloy system.
DETAILED DESCRIPTION
[0012] Braze alloys designed for brazing high temperature
components such as SiC/SiC ceramic matrix composites (CMC) have
been developed. The new braze alloys melt at lower temperatures
than previous generations of high temperature braze alloys, yet
result in brazed joints with high joint strengths and good
stability during elevated temperature use. In addition, the new
braze alloys exhibit good flow properties and wettability with CMCs
and may be useful with other materials, such as metals. Initial
studies indicate that reactions between the braze alloy and the CMC
during brazing lead to stable phases that do not detrimentally
affect the mechanical properties of the brazed joint. For example,
brazed joints fabricated using the new braze alloys exhibit high
shear strengths.
[0013] Suitable braze alloys may have a braze composition including
silicon at a concentration from about 48 atomic percent (at. %) to
about 66 at. %, titanium at a concentration from about 1 at. % to
about 35 at. %, and one or more additional elements selected from
among aluminum, cobalt, vanadium, nickel, and chromium. The
additional element(s) may account for the balance of the braze
composition, except for any incidental impurities. The melting
temperature of the braze composition is less than 1300.degree. C.
Preferably, the melting temperature is at least about 1150.degree.
C.
[0014] The braze composition may be a silicon-rich alloy that
includes either aluminum, cobalt or titanium in an amount ranging
from about 27 at. % to about 36 at. %. Generally speaking, the
braze composition may comprise silicon as the primary constituent
in terms of concentration, with either aluminum, cobalt or titanium
as the secondary constituent. Three exemplary braze compositions
having reduced melting temperatures are identified in Table 1.
Suitable brazing temperature ranges for the braze compositions are
also proposed. Typically, brazing is carried out at a temperature
("brazing temperature") higher than the melting temperature of the
braze composition. For example, the brazing temperature may be at
least 40.degree. C. higher than the melting temperature, or at
least 80.degree. C. higher than the melting temperature. The
brazing temperature may also be up to 100.degree. C. higher than
the melting temperature, or up to 140.degree. C. higher than the
melting temperature.
TABLE-US-00001 TABLE 1 Braze Compositions with Reducing Melting
Temperatures Compo- sition Melting Brazing Range Temperature
Temperature Braze Composition Element (at. %) (.degree. C.)
(.degree. C.) (1) Si--Al--Ti Si 60-66 1150-1185 1210-1310 Al 32-36
Ti 2-4 (2) Si--Co--V--Ti Si 59-63 1225-1260 1280-1335 Co 27-30 V
7-10 Ti 1-3 (3) Si--Ti--Ni--Co--Cr Si 48-52 1270-1295 1310-1350 Ti
29-35 Ni 7-11 Co 4-6 Cr 3-6
[0015] Referring to Table 1, the braze composition may include
silicon, titanium and aluminum. Alternatively, the braze
composition may include silicon, titanium, cobalt and vanadium, or
the braze composition may include silicon, titanium, nickel, cobalt
and chromium.
[0016] In a first example, the braze composition may include
aluminum at a concentration from about 32 at. % to about 36 at. %.
The concentration of silicon may be from about 60 at. % to about 66
at. %, and the concentration of titanium may be from about 2 at. %
to about 4 at. %. The melting temperature may lie in a range from
about 1150.degree. C. to about 1185.degree. C. In one particular
example, the braze composition may comprise 63 at. % Si, 34 at. %
Al and 3 at. % Ti.
[0017] In a second example, the braze composition may include
cobalt at a concentration from about 27 at. % to about 30 at. %.
The concentration of silicon may be from about 59 at. % to about 63
at. %, and the concentration of titanium may be from about 1 at. %
to about 3 at. %. The braze composition may further comprise
vanadium at a concentration of from about 7 at. % to about 10 at.
%. The melting temperature may lie in a range from about
1225.degree. C. to about 1260.degree. C. In one particular example,
the braze composition may comprise 61 at. % Si, 29 at. % Co, 8 at.
% V and 2 at. % Ti.
[0018] In a third example, the braze composition may include
titanium at a concentration from about 29 at. % to about 35 at. %,
and the concentration of silicon may be from about 48 at. % to
about 52 at. %. The braze composition may further comprise nickel
at a concentration from 7 at. % to about 11 at. %, cobalt at a
concentration from about 4 at. % to about 6 at. %, and chromium at
a concentration of from about 3 at. % to about 6 at. %. The melting
temperature may lie in a range from about 1270.degree. C. to about
1295.degree. C. In one particular example, the braze composition
may comprise 50 at. % Si, 32 at. % Ti, 9 at. % Ni, 5 at. % Co and 4
at. % Cr.
[0019] The braze alloy may include one or more of the three
exemplary braze compositions described above and in Table 1. When
the braze alloy includes two or more of the exemplary braze
compositions, a suitable braze temperature may be selected based on
the braze temperature ranges provided in the table in view of the
proportion of each braze composition included in the braze alloy.
Suitable proportions in the braze alloy may be, for example, at
least about 30 wt. % or at least 50 wt. % of one of the braze
compositions, and no more than about 70 wt. % or no more than about
50 wt. % of another of the braze compositions. In some cases, the
braze alloy may also or alternatively include added constituents,
such as silicon or another element or alloy in combination with the
first, second and/or third exemplary braze composition(s). For
example, the braze alloy may include at least about 50 wt. % or at
least about 70 wt. % of the one or more of the exemplary braze
compositions described in this disclosure, with the balance of the
braze alloy (e.g., about 50 wt. % or less, or about 30 wt. % or
less) being the added constituent, such as silicon.
[0020] The braze composition may include, particularly once brazing
has been carried out, at least one silicide phase, such as, for
example, TiSi.sub.2, CoSi.sub.2, VSi.sub.2, (Ni,Co)Si.sub.2,
(Ti,Cr)Si.sub.2, and/or Ti.sub.4Ni.sub.4Si.sub.7. Such phases may
be thermally stable and nonreactive with the CMC and may lead to
good mechanical properties of the brazed joint. For example, a
braze alloy comprising 63 at. % Si, 34 at. % Al and 3 at. % Ti as
described above may include TiSi.sub.2 in the form of a small,
cellular phase. Based on initial testing, the apparent shear
strength of a brazed joint comprising comprising this braze alloy
is 35 MPa, nearly six times higher than that measured for a
previously developed 75 wt. % Si-25 wt. % Ti alloy (85.3 at. %
Si-14.7 at. % Ti alloy).
[0021] As an example of a method of using the braze alloy, the
braze alloy may be employed to join a first component to a second
component, where each component comprises a ceramic matrix
composite, such as a SiC/SiC composite, or another material, such
as a metal. Thus, the braze alloy may be employed to bond a CMC to
a CMC, or a CMC to another material, such as a metal. The braze
alloy may be used in the form of a rod, ribbon, wire, powder, paste
or slurry. The braze alloy, which comprises a braze composition
having any of the characteristics described in this disclosure, may
be placed adjacent to and/or between the first and second
components, either prior to heating or during the heating process.
The braze alloy is then heated to the desired brazing temperature,
which, as explained above, is typically higher than the melting
temperature of the braze composition. Typically, the brazing
temperature lies in a range from about 1210.degree. C. to about
1350.degree. C. The braze alloy may be maintained at the desired
brazing temperature for a predetermined amount of time, followed by
cooling, typically to room temperature, in order to form a
solidified brazed joint between the first component and the second
component. The brazed joint may include any of the silicide phases
set forth above. In some cases, after brazing, the brazed joint may
be subjected to a diffusion heat treatment at a suitable
temperature, such as between about 1090.degree. C. and about
1315.degree. C.
[0022] A thermodynamic and microstructural analysis of the
exemplary braze alloy systems proposed in this disclosure
(Si--Al--Ti, Si--Co--V--Ti, and Si--Ti--Ni--Co--Cr) is carried out
using thermodynamic modeling software (Thermo-Calc), scanning
electron microscopy (SEM) and energy dispersive spectroscopy (EDS).
The braze alloys can be fabricated by melting raw material stock
(e.g., metal powders or chunks) in the appropriate composition
ratios in an arc button melter or other melting apparatus. Liquidus
(melting) and brazing temperatures are determined from the
thermodynamic analysis as well as actual melting and brazing
experiments, and are summarized in Table 1 above.
[0023] Thermodynamic modeling results for the Si--Al--Ti system are
shown in FIGS. 1A-1D, with Al additions to the Si--Ti system of 10
at. %, 20 at. %, 30 at. %, and 35 at. %, respectively. As the Al
content increases in the Ti--Si system, the liquidus temperature
(or melting point) decreases from 1285.degree. C. to 1163.degree.
C., as indicated in the phase diagrams. As temperature decreases,
the Ti--Si eutectic structure forms in the system once the
temperature reaches the eutectic temperature (dashed line). After
that, the Ti--Si eutectic continues to form until the temperature
reaches 577.degree. C. A suitable braze composition determined by
thermodynamic modelling is 3 Ti-35 Al-62 Si (in at. %) or 5.08
Ti-33.39 Al-61.53 Si (in wt. %). According to the thermodynamic
analysis, phases present in the braze composition include silicon
(diamond structure), aluminum and TiSi.sub.2. The presence of
silicon, aluminum, TiSi.sub.2 and Al--Si eutectic is verified by
EDS and SEM. Silicon is found to take the form of a coarse columnar
phase, TiSi.sub.2 is present as a small cellular phase, and the
Al--Si eutectic structure can be found between the coarse silicon
phases.
[0024] Thermodynamic modeling results for the Si--Co--V system are
shown in FIGS. 2A-2C, and for the Si--Co--V--Ti system in FIGS.
3A-3C. By adding 10 wt. %, 30 wt. % and 50 wt. % V into the Co--Si
binary system where Co:Si=1:1 (wt. %), the liquidus temperature
changes from 1061.degree. C. (10 wt. % V) to 1144.degree. C. (30
wt. % V), and finally reaches 1168.degree. C. (50 wt. % V), as
indicated in the phase diagrams of FIGS. 2A-2C, respectively. Thus,
a low V concentration (e.g., Co:Si:V=4:4:1) is selected for
thermodynamic analysis of a quaternary system including silicon,
cobalt, vanadium and titanium. In the Si--Co--V--Ti analysis, Ti is
added into the system in amounts of 1 wt. %, 5 wt. % and 10 wt. %
as a minor ingredient, and the liquidus changes to 1194.degree. C.,
1209.degree. C. and 1425.degree. C., respectively, as shown in the
phase diagrams of FIGS. 3A-3C, respectively. Thus, a suitable braze
composition is selected to be Si=61 at. %, with Co:Si:V=4:4:1 in
wt. %; that is, 43.7Co-43.7Si-10.92V-1.68Ti (in wt. %) or
29Co-61Si-8V-2Ti (in at. %). The thermodynamic analysis shows the
presence of Si (diamond), TiSi.sub.2, Co--Si solid solution (at low
V content) and V--Si solid solution (at low Co content). EDS
mapping reveals three main phases in the braze alloy, including
VSi.sub.2, CoSi.sub.2, and silicon. Some Ti-rich areas are also
detected using EDS mapping; according to the thermodynamic
analysis, the Ti-rich phase may be TiSi.sub.2.
[0025] SEM and EDS analyses reveal details about the microstructure
of the Si--Ti--Ni--Co--Cr system. Several silicides, including
(Ni,Co)Si.sub.2, (Ti,Cr)Si.sub.2 and Ti.sub.4Ni.sub.4Si.sub.7, as
well as silicon are identified in the braze alloy. At the interface
between the braze alloy and the SiC substrate, the
(Ti,Cr).sub.5Si.sub.3 phase is found, which has much higher Cr
concentration than that of the (Ti,Cr)Si.sub.2 phase found in the
braze alloy. In the reaction zone, the (Ni,Co)Si.sub.2 and
(Ti,Cr)Si.sub.2 phases are also detected.
[0026] To clarify the use of and to hereby provide notice to the
public, the phrases "at least one of <A>, <B> , . . .
and <N>" or "at least one of <A>, <B> , . . .
<N>, or combinations thereof" or "<A>, <B> , . .
. and/or <N>" are defined by the Applicant in the broadest
sense, superseding any other implied definitions hereinbefore or
hereinafter unless expressly asserted by the Applicant to the
contrary, to mean one or more elements selected from the group
comprising A, B , . . . and N. In other words, the phrases mean any
combination of one or more of the elements A, B , . . . or N
including any one element alone or the one element in combination
with one or more of the other elements which may also include, in
combination, additional elements not listed.
[0027] Although considerable detail with reference to certain
embodiments has been described, other embodiments are possible. The
spirit and scope of the appended claims should not be limited,
therefore, to the description of the preferred embodiments
contained herein. All embodiments that come within the meaning of
the claims, either literally or by equivalence, are intended to be
embraced therein.
[0028] Furthermore, the advantages described above are not
necessarily the only advantages, and it is not necessarily expected
that all of the described advantages will be achieved with every
embodiment.
* * * * *